By way of example, one fault testing apparatus is disclosed in U.S. Pat. No. 3,728,616. This apparatus tests for wiring errors in connections between various pairs of terminals. The apparatus includes a plurality of pairs of matched resistors with one pair of terminals connected in series between each respective pair of resistors. Each series connection is across a voltage source. The voltage across one resistor of each pair is sensed by a detector, a separate different detector corresponding to each resistor pair, to determine the voltage above or below a predetermined range of voltages at each resistance pair representing a defectively wired circuit. Each pair of matched resistors has values differing sufficiently from the values of every other pair of resistors to enable detection of crossed or erroneous connections. In multiconductor cables having a large number of conductors, for example 50 to 100 conductors, such a test apparatus becomes relatively costly and complex due to the relatively large number of corresponding differing resistance values and detectors employed.
Further, a power supply is provided having a number of different voltage outputs. The disclosed detector circuit employs five different voltages, by way of example. Employing a plurality of voltage supplies also is relatively complex and costly to implement.
A cable tester for locating shorts and discontinuities in multiconductor cables is disclosed in U.S. Pat. No. 4,227,146. There are open and short circuit detectors disclosed, each conductor under test having a separate set of open and short detector lights. For a large number of cables, for example 50 conductors or more, the disclosed system would therefore require at least 100 indicating lights. Such a large number of lights are difficult to manually scan to determine a fault condition on a repetitive basis for long periods of time and is visually fatiguing.